The goal of the proposed research is to develop diverse psychometrically sound cognitive markers of the predisposition to schizophrenia. The research plan focuses on solutions to psychometric problems because such problems appear to be a major obstacle in this area. The tasks chosen are ones that appear especially promising for measuring important but separate aspects of schizophrenic cognitive defect and that seem suitable for measuring the mild degree of cognitive defect that is expected in the nonpsychotic relatives of psychotic patients. The measures are: 1) associatively based semantic priming, a phenomenon that reflects persistence of associative arousal; 2) a version of the span-of-apprehension task, which measures attentional breadth and possibly controlled allocation of attentional resources; 3) defective comprehension in binaural listening which is thought to reflect defective interhemispheric transfer; 4) the Navon task which measures the failure to inhibit responses to material that should be screened out to facilitate cognitive processing; and 5) a version of the Place and Gilmore task which measures an aberrant perceptual response to groupings of stimuli. The psychometric problems of special concern are: 1) the artifactual curvilinear relationship in measures of differential deficit, for Tasks A and B, between the (A - B) difference score and the (A + B) score of overall accuracy, and 2) the effects of differential discriminating power of the two tasks coupled with differences among subjects in overall accuracy in yielding artifactual difference scores. The design solutions will be either the use of psychometrically matched tasks or the use of titration in which (A + B) overall accuracy is maintained at a constant level by manipulation of an appropriate stimulus variable. Schizophrenic, schizophreniform, and bipolar patients will be tested as well as relatives of schizophrenic and schizophreniform patients and control subjects. Schizophrenics will be tested at different stages of their illness and both on-drug and drug-free patients will be included.